Book/Report

FZJ-2019-01278

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Mesonen im Nukleon und ihre Auswirkungen in elastischer und tief-inelastischer Streuung

Holtmann, H. (Corresponding author)FZJ*

1995
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/21560

Report No.: Juel-3166

Abstract: New experiments have shown that the structure of the nucleon is much more complicated than previously expected. The measurement of the Gottfried Sum Ruleleads to the unexpected conclusion that the customarily assumed symmetry among the sea quarks of the nucleon, $\overline{u}(x) = \overline{d}(x)$, is not fulfilled. This symmetry is a direct consequence of perturbation theory; thus in the explanation of this symmetry breaking non-perturbative physics must be involved. In this report the well-known not ion of a mesonic cloud surrounding the nucleon is used. For the description of this mesonic cloud all mesons which are of importance for N N scattering are considered, i.e. the $\pi, \eta, \rho$ and $\omega$. To be able to analyse effects of components carrying strangeness the K and K* mesons are also included. The remaining nucleonic core can be a N, $\Delta, \Sigma, \Lambda$ or $\Sigma$*. All parameters needed for practical calculation aretaken from the N N- and Y N-potentials and from the high energy inclusive n, $\Lambda$ and $\Delta^{++}$-production cross section in pp-scattering. The value obtained for the Gottfried Sum Rule using these parameters is consistent with the experimental result. Furthermore, we analyse what kind of experiments are suitiable for the extraction of the Bjorken-x dependence of the $\overline{u}$ - $\overline{d}$ asymmetry. One of the best candidates is the Drell-Yan asymmetry. The first measurement of this quantity agrees very well with the prediction of the model presented here. Moreover, we present a novel method for measureing the structure functions of the pion. An intrinsic factorization property of the semi-inclusive neutron production cross section needed for this measurement gives good control over all model assumption needed for the extraction of the pion structure function. In the remaining part of this report we analyse the influence of the mesonic cloud on the electromagnetic properties of the nucleon. In contrast to earlier calculations we do not use any simplifing assumptions in treating the recoil of the nucleon when emitting a meson. Thus we can calculate the influence of the mesonic eloud up to quite high momentum transfers reliably. Indeed the contributions from the mesonic cloud survive up to a moment um transfer of 10 - 15 GeV$^{2}$.•

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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